1. Field of the Invention
The invention relates to a cardan ball suspension.
2. Description of the Related Art
Conventional ball suspensions are used to align a particular point of the spherical surface over a spherical angular range. In conventional cardan ball suspensions this requires two articulations or a double articulation in order to set any spherical angle within a certain spherical angle range.
A ball suspension or a universal ball joint suspension associated with an intrusion protection detector, wherein the sensor of the detector is arranged in the ball or the spherical cap concentrically surrounding the sensor opening is shown in EP-A-12280. The sensor opening may be pivoted over a certain spherical angle range into all directions by rotating the spherical cap in a supporting layout. Rotation of the ball in relation to the sensor axis or the normal to the sensor surface is possible and unavoidable during such pivoting of the spherical cap.
Axial rotation of a ball suspension and sensor, detector, or reflector surface is acceptable only if the surfaces or the beams emitted by the surface or impacting it are symmetrical in rotation when sensors or other devices such as detectors, reflectors, or the like are used in combination with a ball suspension. A conventional suspension is not suitable for adjustment and aligning of a device used in combination with a ball suspension if there is no rotational symmetry or different symmetries prevailing in connection with the surfaces or beams.
Space monitoring indicating devices typically comprising more than one, preferably two, sensors for electromagnetic radiation and, in particular, infrared radiation are radiating or receiving devices which do not exhibit rotational symmetry. If two emitters or detectors are used in combination, there is no rotational symmetry with respect to the emitter or rotation axis but rather a plane symmetry. Emitters or detectors housed in tubes with rectangular cross sections wherein at least two opposing internal surfaces and directed onto one or several sensors, again are not devices exhibiting rotational symmetry. An indicating device of this type is shown in DE-B No. 26 53 110. Conventional ball or universal ball joint suspensions are not suitable for use in combination with non-rotationally symmetrical sensors, detectors or emitters. During adjustment or setting or pivoting the ball or spherical cap of a conventional suspension, rotation around the sensor, detector, or emitter axis occurs and cannot be prevented.